American food is usually hybrid food based on other cultures, either with american ingredients (potatos, tomatos, peppers) or multiple cultures blending together.
Some that I would think should be considered good american food:
smoked/BBQ, Cajun food, generally Southern Cooking, American Chinese food, Tex Mex, Lobster and sorta all those northeastern cuisines, hamburgers and hotdogs.
I don't know why people think America does food bad, we're not one of the fattest countries because our food sucks.